Comparative evaluation of the kinematic parameters at symmetric and asymmetric cold rolling of strip using computer simulation

Computer simulation of symmetric and asymmetric cold rolling of AISI-1008 steel strip in three passes was carried out. DEFORM finite element method (FEM) software was used for computer simulation. Technique allowing neutral line location determination was designed and this technique is based on the processing of FEM computer simulation results. Neutral line location during each of three passes at different working roll diameters combinations (symmetric rolling, rolling with 0.83 %, 1.67 % and 5 % working rolls diameters asymmetry) was detected using designed technique. It was established that working rolls diameters asymmetry increase till 5 % moves the middle of the neutral line towards rolling direction in 0.250 mm for the first pass, 0.199 mm - for the second pass, 0.133 mm for the third pass. That is, influence of working rolls diameters asymmetry increase becomes weaker with the decrease of absolute value of height reduction. Three-dimensional graphs were made: one is illustrating dependence of position of the neutral line's midpoint from rolling speed and working rolls diameters asymmetry and the other one is illustrating dependence of the neutral line inclination angle from rolling speed and working rolls diameters asymmetry. Weak direct correlation between working rolls diameters asymmetry and position of neutral line's middle point and strong direct correlation between rolling speed and position of neutral line's middle point were detected. Velocity diagrams along vertical lines in lag zone and lead zone of the deformation zone at asymmetric rolling show that velocity at point of contact of upper roll and strip is less than velocity at point of contact of lower roll and strip.